The extent to which medically prescribed drugs and illicitly obtained substances are taken habitually, either alone or in various combinations, is not matched by the extent of the systematic information available on the behavioral effects of these drugs and drug combinations. This project is an attempt to more fully characterize the behavioral effects of narcotic analgesics (such as morphine), their pharmacological antagonists (such as naloxone), and interactions in the behavioral effects of these drugs with representative psychoactive agents of other classes (antidepressants, neuroleptics, barbiturates, benzodiazepines). The focus is on schedule-controlled behaviors in squirrel monkeys, rats, and pigeons. These behaviors are maintained by food water presentation or by termination of electric shock. The effect of both acutely and chronically administered drugs and drug combinations will be studied. It is our hope that results from the broad range of experiments undertaken in this project will be of value in predicting and understanding the likely effects of widely used and abused drugs in human populations.